GB1573242A - Filling amould with a predetermined quanitity of molten metal - Google Patents

Description

PATENT SPECIFICATION

( 21) ( 31) Application No 9805/77 Convention Applicaton No.

3169176 ( 11) 1 573 242 ( 22) Filed 8 March 1977 ( 32) Filed 15 March 1976 in ( 33) Switzerland (CH) ( 44) Complete specification published 20 Aug 1980 ( 51) INT CL 3 B 22 D 39/04 G 05 D 9/121/ B 22 C 9/08 ( 52) Index at acceptance G 3 R A 273 A 33 B 23 BT 2 B 3 F 11 P 4 G 1 W B 2 ( 54) FILLING A MOLD WITH A PREDETERMINED QUANTITY OF MOLTEN METAL ( 71) I, ERWIN BUHRER, of Swiss nationality, of Vogelingasschen 40, 8200 Schaffhausen, Switzerland, do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly descirbed in and by the following statement:-

The present invention relates to the filling of molds with a predeterminzd quantity of molten metal.

According to one aspect of the present invention there is provided a method of filling a mold with a predetermined quantity of molten metal from a receptacle, the method comprising continuously monitoring the pressure head of the molten metal in the receptacle above a bottom opening which is open during filling of a mold to supply molten metal to the mold, integrating a signal derived from the pressure head and corresponding to the flowrate of molten metal through the bottom opening, and closing the bottom opening when the integral of the signal reaches a predetermined value, the flow cross-section of the bottom opening remaining substantially constant during filling of a mold.

According to another aspect of the present invention there is provided apparatus for filling a mold in accordance with the method just defined, the apparatus comprising: the receptacle with the bottom opening which is closable by a plug; means for continuously monitoring the pressure head of molten metal in the receptacle above the bottom opening; a voltage-frequency transducer for producing pulses at a frequency which is a function of the monitored pressure head; a digital counter for counting pulses from the transducer and provided with a memory for storing the predetermined value for the integral of the signal; and means for automatically actuating the plug to close the bottom opening when the predetermined value is reached.

For a better understanding of the present invention and to show how it may be carried into effect, reference will now be made, by way of example only, to the accompanying 50 drawings, in which:

Fig 1 is a sectional view of apparatus for filling molds, taken along a line I-I in Fig 2; Fig 2 is an elevation of the apparatus as viewed in the direction of an arrow II shown 55 in Fig 1; Fig 2 a is a detailed elevational view, partially in section, showing an alternative embodiment; Fig 3 is a sectional view showing a detail 60 of a portion of the apparatus depicted in Fig.

1 on an enlarged scale; Fig 4 is a top view of a support for a molten metal receptacle of the apparatus; Fig 5 is a graph showing a curve repres 65 enting the relationship between the pressure head of molten metal in a receptacle and the outflow velocity thereof; Fig 6 is a block diagram showing electronic circuitry for controlling the apparatus 70 of Figs 1 to 4; and Fig 7 is block diagram showing another embodiment of the electronic circuitry.

Referring now to the drawings wherein like reference numerals refer to similar parts 75 throughout the various figures thereof, an apparatus embodying the present invention is shown as comprising a receptacle or tank 1 which contains molten metal casting material 2 and includes pouring means compris 80 ing a bottom opening 3 which may be opened and closed by a plug 4 In the preferred form of the invention, opposite ones of the inner walls 83, 84, 85 and 86 of the receptacle 1 are formed to be parallel with 85 each other so that the weight of the liquid metal within the receptacle will rise in direct proportion to the filling height so that the latter can be determined by a weighing operation 90 c C 4 en t_ tn "M 1 573 242 The bottom opening 3 tapers towards its lower end and preferably at the discharge end 104 it has its smallest cross section In this way, a defined bottleneck is provided and a compact molten metal jet 103 may be obtained.

Lifting gear 5 for raising and lowering the operating plug 4 is provided which is capable of receiving compressed air through a pressure line 6, a valve 7 and a line 8 As a result, the plug 4 may be raised into the position shown in Fig 1 by operation of the valve 7 By reversing the valve 7, to connect line 8 with an exhaust pipe 9, the plug may be lowered into the position shown in Figs 2 and 3 and the bottom opening may be thus closed.

An electric switch 10 is provided which is actuated by a bar 11, rigidly connected with the plug 4, when the bottom opening 3 opens The bar 11 when in the raised position will actuate the switch 10 as shown in Fig 1 When the plug 4 is lowered in the position indicated in Fig 2, the electric switch 10 will again be released.

A filling opening 13 having a cover 12 is provided for replenishing the tank or receptacle 1 The tank 1 is supported upon a floor surface 15 by means of a supporting construction 14 which is shown in Figs 1 and 4.

The tank 1 has a flange 16 which bears upon a support 17 The tank also has a flange 18 which bears upon a weighing device in the form of a pressure cell 19, with the bottom 20 of the tank being supported by a rigid support member 21 Thus, it will be seen that the support arrangement provides a three-point support which is illustrated in Fig 4 and which thereby ensures that the pressure cell 19 will receive a load force which is proportional to the total weight of the tank 1 and the molten metal 2 in it.

It is advantageous to locate and arrange the support member 21 relative to the filling opening 13 so that the support member 21 is located directly under the molten metal jet which is formed during the filling or replenishing of the tank 1 In this manner, the measured value of the pressure cell will remain uninfluenced by the momentum or force of the jet pressure when the tank 1 is replenished.

The apparatus is designed so that molds which are to be filled may be successively moved into positions beneath the tank 1 In the drawings, and with particular reference to Fig 2, a mold 25 is shown in the pouring position below the tank 1 Additionally, a mold 22 is shown in the position just prior to the pouring position and a filled or poured mold 26 is shown after having been passed from the pouring position with all of the molds being arranged for conveying upon a roll-out or conveyor table 27 The mold 25 in the casting position receives molten metal through a pouring spout 29 which defines a passage through which the metal may be made to flow from the tank 1 into an upper trough 31 and from there into a series of through gates 32 and subsequently into the 70 cavity of mold 25 The pouring spout 29 is arranged so that it will bear upon the top of the mold 25 during the pouring operation.

After pouring is completed, the spout 29 may be tilted about a rotary shaft 35 and it 75 will thus be lifted off the top of the mold 25 by means of a reversing gear (not shown) of a cylinder 33 and it will be brought into a position labelled 34 A beam 36 supports the rotary shaft 35 and cylinder 33 by means 80 of a support structure 37 of the conveyor table 27 upon a floor surface 15.

Located above a position where poured molds are brought out from under the tank 1, there is provided a remote sonic sensor 38 85 which operates to sonically measure the height 40 of a riser 105 in a poured mold such as the mold 26 The measured value sensed by the sonic sensor 38 is transmitted to an electronic control element 41 In 90 another embodiment of the invention, the riser height 40 may be sensed by a photocell 42 as depicted in Fig 2 a.

Fig 5 shows a curve 43 which depicts the relationship between the outflow velocity of 95 the liquid metal and its pressure head Outflow velocity is represented along the ordinate 44 and the pressure head above the discharge opening in the tank 1 is represented along the abscissa 45 The curve 43 100 is a parabola The values of pressure head in the tank 1 are indicated at 46, 47, 48, 49 and 79 along the curve 43 and each of these points correspond, respectively, to molten metal levels 23, 34, 50, 56 and 51 depicted 105 in Fig 3.

As depicted in curve 43, and outflow velocity of value 52 corresponds to a pressure head of value 47 Other relationships will be apparent from the graph of Fig 5 For 110 example, outflow velocity 53 corresponds to pressure head 48, 64 corresponds to 49, and 54 corresponds to 79.

Experience has shown that slag formation occurs on the surface of the molten metal 115 Therefore, care must be taken in the operation of the pouring mechanism to ensure that, on the one hand, the amount of liquid metal 2 in the tank 1 does not recede below a minimum level indicated at 50 because the 120 slag on the surface of the molten metal may partially or completely clog the bottom opening of the tank 1 when the tank 1 is allowed to run completely empty On the other hand, the amount of molten metal 2 125 must not exceed the maximum level 51 since the slag or metal entering the clearance 55 between the plug 4 and the tank 1 can solidify thereby making operation of the plug impossible 130 1 573242 Level 56 represents an average molten metal level during operation Since the levels suitable for operation will fall between levels 50 and 51, only the part of the curve 43 between the pressure head values 48 and 79 is of interest with regard to further considerations involved in the description herein The point 53 on the curve 43 represents the minimum outflow velocity and the point 54 represents the maximum outflow velocity of the liquid metal during operation, in view of the considerations discussed above.

In the operation of the apparatus the molds 22, 25 and 26 are passed beneath the tank I in the manner previously described.

The molds move in the direction of the arrow 28 shown in Fig 2, and the mold 26 is shown in the post-pouring position When the molds 22 25 and 26 reach the end of the travel in the direction of arrow 28, a switch (not shown) is operated by the displacement drive of the molds at the end of their displacement path and by operation of the switch there occurs a reversal of the position of the cylinder 33 by means of the valve thereby tipping or rotating the pouring spout 29 from the raised position 34 into position 80 in which the spout bears upon the mold in the pouring position; in the case of Fig 2 this is the mold 25.

At the same time" the valve 7 is actuated or reversed by another switch (not shown) so that the valve 7 line 8, the lifting gear 5 all receive compressed air through pressure line 6 in order to raise the plug 4 from its lowermost position shown in Figs 2 and 3 into the position corresponding to that shown in Fig 1.

As a result of the lifting of plug 4, the bottom opening 3 is open so that pouring of the mold as described above may be initiated By means of electronic circuitry, whose operation will be hereinafter described in greater detail, the pouring operation is completed by reversing the position of the valve 7, lowering the lifting gear and closing the bottom opening 3 by operation of the plug 4 as shown in Fig 3 Subsequently valve 7 is likewise reversed to operate cylinder 33 and spout 29 is lifted from position 80 into the raised position 34.

When spout 29 reaches the position 34, the displacement drive of the molds is started thereby moving the entire mold row by one mold division in the direction of the arrow 28 The working cycle thus commences once again.

The electronic circuitry shown in the block diagram of Fig 6 includes as a central control element a counter 69 which is preferably designed as a reversible counter.

Before the apparatus is started, a memory register 68 is set by a manually operated presetting device 67 to a predetermined value corresponding to the amount of molten metal required by each mold The counter or reversible counter 69 is thus likewise set to this value through a connecting line 82 If, when the apparatus is first 70 started, it is found that this value is not accurate, it may be corrected by the presetting means 67 The reading of the electronic control 41 of the pressure cell 19 must be so calibrated that when the tank is empty, a 75 weight is indicated which will correspond to a falling height of tank 1 on the order of the difference of height 23 to bottom of height 24 This ensures that the measured value of the electronic control 41 of the pressure cell 80 19 is proportional to the pressure head above bottom opening 3.

When the bar 11 actuates the switch 10 as the plug 4 rises at the start of the casting operation, the switch 10 produces a signal 85 which is transmitted to a start-stop logic circuit 61 by a connecting line 87 A gate circuit 62 then receives a signal from a connecting line 88 A signal 63 from the pressure cell 19 is transmitted along a connect 90 ing line 89 to a pre-amplifier 65 and along a connecting line 90 to a voltage-frequency transducer 66 The voltage-frequency transducer 66 generates pulses whose frequency is proportional to the square root of the 95 signal 63 from the pressure cell 19 These pulses are fed through connecting lines 90 and 91 to the counter 69 during the casting operation When the predetermined value set by the presetting device 67 is reached by 100 the counter 69, the counter 69 stops the start-stop logic circuit 61 by means of a signal transmitted through a connecting line 92, a detector 70 and connecting lines 93 and 94 The counter 69 also switches the 105 valve to exhaust thus finishing the casting operation If the counter 69 is designed as a reversible counter and detector 70 as a zero counter, the control will be greatly simplified 110 If the bottom opening 3 changes during a casting sequence due to erosion or slag deposit for example, the presetting means 67 must transmit an adjusted predetermined value to the memory register 68 115 The quantity of molten metal may also be approximately controlled by effecting the control in accordance with a line 95 shown in Fig 5 For this approximation method, the reading of the pressure cell 19 must be 120 so calibrated that, when the tank 1 is empty, a weight will be indicated which corresponds in Fig 5 to the distance between the points 47 and 96, and the voltage-frequency transducer 66 must generate pulses which are 125 directly proportional to the value measured by pressure cell 19.

A second embodiment of the electronic circuitry is depicted in the block diagram of Fig 7 In this sytem, many of the elements 130 1 573 242 shown are identical with elements in Fig 6.

For example, the functions of the elements identified by reference numerals 60, 61, 62, 63,65,66,67 69, 70 82,87,88,90,91,92, 93 and 94 remain unchanged and are the same as in the block diagram in accordance with Fig 6 They are therefore not again described in reference Fig 7 Fig 7 shows a control which automatically accounts for variations in the flow rate of the molten metal through the bottom of opening 3 for a given pressure head The reading of the sensor 38 is transmitted by the electronic control 41, as a signal 72 in Fig 7, through a connecting line 98 to the differential amplifier 73 The difference between these two signals is fed through a connecting line 99 to an analog-digital converter 74 and from there through a connecting line 100 to an add-substractor 75 which also receives the predetermined value from the memory 68 through a line 102 A modified predetermined value is transmitted to the counter 69 through the line 82 and to the memory 68 through a line 101 For example, if the signal representing the height 40 of the riser indicates that an amount less than that corresponding to the desired value 71 has occurred, the predetermined value in the memory 68 is increased That is, the discharge time is extended correspondingly for the next casting operation; conversely, the casting time is decreased when the riser height 40 is too great.

Figs 6 and 7 show specific embodiments of the electronic circuitry The quantitative determination of the molten metal quantity during casting is not, however, confined to these embodiments and the numerical integration can also be effected with other circuits.

The apparatus can be used, as shown, for filling a single large mold or for filling simultaneously several small molds through several closeable bottom openings 3 of a tank 1.

The determination of the molten metal level in the tank is not confined to a weighing operation but it may also be effected for example with devices such as laser beams directed at ceramic bodies which float on the molten metal or over adjustable filling level indicators which work with isotopes.

Claims (1)

1. WHAT I CLAIM IS:-

   1 A method of filling a mold with a predetermined quantity of molten metal from a receptacle, the method comprising continuously monitoring the pressure head of the molten metal in the receptacle above a bottom opening which is open during filling of a mold to supply molten metal to the mold, integrating a signal derived from the pressure head and corresponding to the flowrate of molten metal through the bottom opening, and closing the bottom opening when the integral of the signal reaches a predetermined value, the flow cross-section of the bottom opening remaining substantially constant during filling of a mold.

   2 A method as claimed in claim 1, in 70 which the height of a riser of a filled mold is measured and any deviation of the measured height from a predetermined height is used to correct the predetermined value of the integral of the signal for a subsequently 75 filled mold.

   3 Apparatus for filling a mold in accordance with the method of claim 1, the apparatus comprising: the receptacle with the bottom opening which is closable by a 80 plug; means for contiuously monitoring the pressure head of molten metal in the receptacle above the bottom opening; a voltagefrequency transducer for producing pulses at a frequency which is a function of the 85 monitored pressure head; a digital counter for counting pulses from the transducer and provided with a memory for storing the predetermined value for the integral of the signal; and means for automatically actuat 90 ing the plug to close the bottom opening when the predetermined value is reached.

   4 Apparatus as claimed in claim 3, in which a weighing device is provided for monitoring the pressure head 95 Apparatus as claimed in claim 4 in which the weighing device includes a pressure cell.

   6 Apparatus as claimed in claim 4 or 5, in which a rigid support member for the 100 receptacle is disposed beneath a filling opening of the receptacle and is spaced horizontally from the axis of the bottom opening and from the weighing device.

   7 Apparatus as claimed in any one of 105 claims 3 to 6 in which the bottom opening tapers in the downwards direction, its smallest cross-sectional area being at the discharge end.

   8 Apparatus as claimed in any one of 110 claims 3 to 7 in which an electrical switch is provided which is actuated by movement of the plug to open to bottom opening, the switch being connected to a start/stop logic circuit for imparting a start signal to the 115 logic circuit.

   9 Apparatus as claimed in any one of claims 3 to 8 in which means are provided for measuring the height of a riser of a filled mold 120 Apparatus as claimed in claim 9 in which the means for measuring the height of a riser comprises a remote sensor.

   11 Apparatus as claimed in claim 9 or in which the means for measuring the 125 height of a riser comprises a photoelectric cell.

   12 Apparatus as claimed in any one of claims 9 to 11, in which correcting circuitry is provided for adjusting the predetermined 130 1 573 242 value of the integral of the signal, the correcting circuitry cmprising a differential amplifier which receives signals corresponding to the measured riser height and to a desired riser height, the output of the differential amplifier being connected via an analog/digital converter to an adder/subtractor which provides a signal for adjusting the predetermined value of the integral.

   13 A method of filling a mold as claimed in claim 1 and substantially as described herein.

   14 Apparatus for filling a mold substantially as described herein with reference to Figures 1 to 4 and to Figures 6 and 7 of 15 the accompanying drawings.

   HASELTINE LAKE & CO.

   Chartered Patent Agents 28 Southampton Buildings Chancery Lane, London WC 2 A 1 AT -andTemple Gate House Temple Gate Bristol B 61 6 PT 9 Park Square Leeds LS 1 2 LH Printed for Her Majesty's Stationery Office by The Tweeddale Press Ltd Berwick-upon-Tweed, 1980 Published at the Patent Office, 25 Southampton Buildings London WC 2 A l AY, from which copies may be obtained.